In areas of moderate to high seismicity, the Uniform Building Code requires large computer units, weighing more than 400 pounds, to be stably restrained so as to prevent these computer units from becoming moving hazards in an earthquake. Moreover, where continuous operation of the computer units is necessary, it is imperative that the units be stably anchored so as to prevent damage to the units themselves in a seismic event.
Until recently, most computers were secured by relatively unsound methods. In the past, computer units were restrained by the electrical cables that feed power into the units, or by bent bars placed around the caster wheels to serve as caster stops. These methods were capable of restraining the units, but did not protect the computer units from damage. Some of these prior seismic restraint methods, however, actually failed to restrain the computer units at all, leading to the hazardous conditions mentioned above.
It is evident that proper seismic restraint for computer units could provide assurances against damage to life and property. Thus, a direct, positive, and calibrated structural anchoring system for large computer units is needed.
A currently utilized seismic restraint system is described in a recent technical publication. See John D. Meyer, S. E., Dr. Tsu T. Soong, Richard H. Hill, xe2x80x9cRetrofit Seismic Mitigation of Mainframe Computers and Associated Equipment: A Case Studyxe2x80x9d, ATC 29-1, 1998, pp. 149-163. This seismic restraint system uses steel cables, turnbuckles, eyebolts and direct, drop-in, concrete anchors. Indeed, this seismic restraint system meets the criteria set for by the Uniform Building Code. This restraint system, however, does not satisfy some of the needs encountered during certain on-site conditions due to the inaccessibility of its connecting subsystem and the rigidity of its fixed anchoring subsystem.
For example, using this prior art seismic restraint system, it is difficult to install the steel cable onto the computer unit because this restraint system requires that the cable be looped through the caster frame. If the space gap between the caster wheel and the caster frame is relatively narrow, it becomes difficult, to nearly impossible, to loop the cable through the caster frame and the wheel. Moreover, due to obstructions in and around the computer units, accessibility to the caster frame system also may be limited.
Further, there is frequently a need to reconfigure the computer units as on site conditions change due to unit model upgrades or to system modifications. However, using the system described in ATC 29-1, computer unit reconfigurations are difficult, or nearly impossible, at the point where the cables are anchored to the concrete slab. This inability to reconfigure the computer units stems from the use of a fixed anchor point in the prior art restraint system. Thus, each time a new computer configuration is desired, new concrete anchors are required to be installed at the reconfigured cable attachment location. Furthermore, in reconfiguring new anchors, new drilling of the concrete slab is required which generates dust that may contaminate the computer units and lead to equipment failure. For facilities where continuous operation is imperative, new drilling for reconfigurations could result in down time of the reconfigured computer units. This down time is generally unacceptable to the end-users. Finally, due to congestion or other conditions at the installation site, utilization of this fixed anchor restraint system may not be possible.
Thus, there(is a need for a seismic restraint tethering system, that would make the attachment of a steel cable to a caster easier and faster. Moreover, there is a need for a seismic restraint system that is capable of being utilized in almost any on-site condition. Above all, there is a need for a new seismic restraint system which is able to accommodate computer unit reconfigurations without re-drilling of the anchoring system.
The present invention is directed towards a seismic-resistant system for large electrical equipment, weighing 400 pounds or more, and located within or on top of buildings. Such large electrical equipment contains electrical components that can be subject to seismic damage. Moreover, the size of the equipment demands that the equipment be restrained so as to prevent moving hazards in a seismic event. Thus, the present invention restrains such equipment preventing damage to life and property in a seismic event.
The large electrical equipment units to be restrained by the seismic restraint system of the present invention includes large, mainframe computer units. When these computer units are housed in:a building, the units are generally located on a floor system, comprising floor tiles, and the floor system is located above a sub-floor, generally comprising concrete. The sub-floor is used as the anchoring point of the seismic restraint system to the electrical equipment.
The seismic restraint system of the present invention further comprises at least two tracks affixed to the sub-floor with fasteners and at least three tie downs. Each tie down of the seismic restraint system comprises: 1) a tethering anchor secured to the track; 2) a connector connected directly to a respective one of the support assemblies; and 3) a flexible wire extending between the tethering anchor and the connector.
Overall, the seismic restraint system of the present invention comprises three subsystems, namely a connector subsystem, a tether subsystem, which together form the tie down of the seismic restraint system, and an anchor subsystem. These subsystems serve to connect, tether and anchor the electrical equipment to the sub-floor.
The major components of the connector subsystem are an axle and an angle bracket for attachment to the bottom housing of computer units via multiple support assemblies. These support assemblies are preferably in the form of casters, comprising a wheel and a caster frame, and are located on the bottom of the computer housing. The caster wheel is usually connected to the caster frame by an axle. This exiting axle, or another axle used in its place, provide a first point of attachment for the seismic restraint system.
The major components of the tether subsystem are a flexible wire, a tension adjuster and a tethering anchor for adjusting the tension on the wire. The tether subsystem provides points of attachment to both the connector subsystem and the anchor subsystem.
The major components of the anchor subsystem are tracks, located on the To sub-floor, and fasteners. These tracks are anchored to the. sub-floor via the fasteners.
Thus, with these three subsystems in place, large electrical equipment can be seismically restrained. Importantly, the seismic restraint system of the present invention is easy to install in any on-site layout and can accommodate reconfiguration of the equipment without redrilling of the concrete sub-floor.
Another aspect of the present invention is a seismic anchoring kit which comprises: 1) tracks for mounting on the sub-floor; 2) fasteners for securely holding the tracks in place on the sub-floor; and 3) tie downs. Each tie down comprises: 1) a tethering anchor which is adjustably securable to one of the tracks; 2) a connector for connection directly to a support: assembly; 3) a flexible wire for placement extending between the tethering anchor and the connector; and 4) a tension adjuster for adjusting the tension on the wire. The seismic restraint kit of the present invention is suitable for use with any electrical equipment, and is particularly suitable for use with large computer units weighing up to 2000 pounds or greater with modifications.
In the seismic restraint system and kit, the tension adjuster is preferably a turnbuckle that is adjustable so that each tie down, which includes the components used to connect and tether the computer unit, has about 0 to 6 inches of play. The kit may further comprise an axle for attachment to the connector. The connecter is preferably an angle bracket which is connected to the axle. Additionally, the kit may comprise a rod for attachment to the connector, or a bent plate, to be used with the angle bracket without use of a rod.
The invention further includes method of anchoring a large electrical equipment via its housing where the equipment is located in, or on, a building, where the building has a floor and a sub-floor. This novel method allows for the attachment of the housing with its multiple support assemblies, located on the bottom of the housing, to the sub-floor.
The seismic restraint installation method of the present invention includes the following:
a) attaching at least two tracks to the sub-floor via fasteners;
b) connecting the connector directly to a wheel assembly;
c) attaching the tethering anchors to the track;
d) attaching the flexible wire from the tethering anchor to one end of a tension adjuster;
e) attaching the flexible wire from the other end of the tension adjuster to the wheel connector; and
f) adjusting the tension on the wire via the tension adjuster. This seismic restraint method can be used with any large electrical equipment, and is particularly suited for use with a large computer.